Lubricators that utilize compressed air, compressed springs, motor driven jack screws, augers or a gas generating cartridge as a driving force to eject lubricant into a machine are known in the prior art. For example, U.S. Pat. No. 4,023,648 to Orlitzky et al. describes a lubricant applicator that electrolytically generates a gas as a driving means to force lubricant out of a chamber into a bearing fitting. U.S. Pat. No. 4,671,386 to Orlitzky describes an applicator in which the required pressure is delivered by a bellows. Automatic control of the lubricating process is shown in U.S. Pat. No. 6,408,985 to Orlitzky et al., which describes a programmable, electrical motor-driven lubricator that in different embodiments forces lubricant from a chamber by the operation of a gear-driven or lever-driven piston, or by a bellows. U.S. Pat. No. 5,732,794 to Orlitzky et al, describes an automated lubricator which is microprocessor controlled and can be programmed to deliver lubricant to a bearing or the like at selected intervals. Operation of the lubricator rests upon the use of a minor pressure imposed by a spring to force lubricant into the threads of an auger, so that rotation of the auger by a motor controlled by the microprocessor then dispenses the lubricant while at the same time providing a mixing action to the lubricant.
There remains a need for portable lubricators capable of supplying a quantity of lubricant quickly, and capable of maintaining a controlled quantity of lubricant over a range of back pressures and ambient temperatures. In some devices, if the back pressure is too high, or the temperature is too low, substantial time may elapse before the lubricant reaches the machinery intended to be lubricated, such as a bearing, and the latter may then become starved for lubricant and suffer damage accordingly. In some gas generating cells, for example, it may take several days to overcome a line resistance of 15 psi before the lubricant actually reaches the point of lubrication. Conversely, under high temperature conditions there is the opposite danger of overlubricating which can also be damaging.